Prostheses for implantation in blood vessels or other similar organs of the living body are, in general, well known in the medical art. For example, prosthetic vascular grafts formed of biocompatible materials (e.g., Dacron or expanded, porous polytetrafluoroethylene (PTFE) tubing) have been employed to replace or bypass damaged or occluded natural blood vessels. A graft material supported by framework is known as a stent-graft or endoluminal graft. In general, the use of stent-grafts for treatment or isolation of vascular aneurysms and vessel walls which have been thinned or thickened by disease (endoluminal repair or exclusion) are well known. Many stent-grafts, are “self-expanding”, i.e., inserted into the vascular system in a compressed or contracted state, and permitted to expand upon removal of a restraint. Self-expanding stent-grafts typically employ a wire or tube configured (e.g. bent or cut) to provide an outward radial force and employ a suitable elastic material such as stainless steel or Nitinol (nickel-titanium). Nitinol may additionally employ shape memory properties. The self-expanding stent-graft is typically configured in a tubular shape of a slightly greater diameter than the diameter of the blood vessel in which the stent-graft is intended to be used. In general, rather than inserting in a traumatic and invasive manner, stent-grafts are preferably deployed through a less invasive intraluminal delivery, i.e., cutting through the skin to access a lumen or vasculature or percutaneously via successive dilatation, at a convenient (and less traumatic) entry point, and routing the stent-graft through the lumen to the site where the prosthesis is to be deployed.
Intraluminal deployment is typically effected using a delivery catheter with coaxial inner (plunger) and outer (sheath) tubes arranged for relative axial movement. The stent graft is compressed and disposed within the distal end of an outer catheter tube in front of an inner tube. The catheter is then maneuvered, typically routed though a lumen (e.g., vessel), until the end of the catheter (and the stent-graft) is positioned in the vicinity of the intended treatment site. The inner tube is then held stationary while the outer tube of the delivery catheter is withdrawn. The inner tube prevents the stent-graft from being withdrawn with the outer tube. As the outer tube is withdrawn, the stent-graft radially expands so that at least a portion of it is in substantially conforming surface contact with a portion of the interior of the lumen e.g., blood vessel wall.
Most stent-graft deployment systems use only a semi-rigid sheath in the deployment systems. The semi-rigid sheath provides columnar strength to advance the system through access vessels in the body. Unfortunately, the semi-rigid sheath may tend to kink in areas having tight radiuses such as the thoracic arch. Such kinking can increase the deployment force required to place a stent-graft in a target area or even prevent deployment completely. Even if kinking can be avoided, use of a semi-rigid sheath may still increase the pushing force needed to overcome frictional resistance required to deploy the stent-graft to the target area.
One attempt to overcome this problem by W. L. Gore utilized a flexible jacket that deploys the stent-graft with a ripcord that opens the jacket along the longitudinal axis of the flexible jacket, e.g., U.S. Pat. No. 6,315,792. Another single step sheath release initiation is disclosed in U.S. Pat. No. 5,824,041 to Lenker. Unfortunately, these methods introduced a separate non-integrated sheath into the system into the femoral artery and further failed to provide the desired control during deployment. Thus, a need exists for a method and deployment system that avoids kinking (reductions in area or change in shape which creates resistance to deployment) and reduces forces during deployment of stent-grafts in areas having tight radiuses, yet provides appropriate control and in addition provides flexibility during advancement in areas having tight radiuses.